Quarterly report pursuant to Section 13 or 15(d)

Equity - Additional Information (Detail)

v3.2.0.727
Equity - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 15 Months Ended
Sep. 30, 2015
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Dec. 31, 2014
Equity [Line Items]              
Minimum number of shares that can be exchanged by exchangeable shareholders unless the number of remaining exchangeable shares registered in the name of the holder is less       50,000      
Number of shares of Common stock received for each exchangeable share       1      
Shares outstanding   198,674,187   198,674,187   198,674,187 210,819,790
Income attributable to the other joint venture members   $ 3,500,000 $ 4,400,000 $ 8,200,000 $ 8,600,000    
Carrying value of the investments held by Quanta in variable interest entities   13,500,000   13,500,000   $ 13,500,000 $ 11,100,000
Carrying value of the investment held by noncontrolling interest in variable interest entities   13,474,000   13,474,000   13,474,000 $ 11,067,000
Distributions to non-controlling interests   2,500,000 $ 0 5,000,000 $ 500,000    
Maximum [Member]              
Equity [Line Items]              
Aggregate authorized amount of common stock to be repurchased   $ 500,000,000   $ 500,000,000   $ 500,000,000  
Treasury Stock [Member]              
Equity [Line Items]              
Treasury stock acquired   5,800,000   12,500,000   15,500,000  
Value of treasury stock acquired, cost method   $ 172,300,000   $ 354,300,000   $ 447,800,000  
Scenario Forecast [Member] | Maximum [Member]              
Equity [Line Items]              
Aggregate authorized amount of common stock to be repurchased $ 1,250,000,000            
Scenario Forecast [Member] | Treasury Stock [Member]              
Equity [Line Items]              
Treasury stock acquired 1,800,000            
Value of treasury stock acquired, cost method $ 52,200,000            
Series F Preferred Stock [Member]              
Equity [Line Items]              
Number of preferred Stock issued to voting trust   1   1   1 1
Series G Preferred Stock [Member]              
Equity [Line Items]              
Number of preferred Stock issued to voting trust   1   1   1 1
Exchangeable Shares [Member]              
Equity [Line Items]              
Shares outstanding   7,325,971   7,325,971   7,325,971 7,325,971
Series F- and Series G- Preferred Stock [Member]              
Equity [Line Items]              
Exchangeable stock shares outstanding   4,399,858   4,399,858   4,399,858  
Common Stock Withheld for Settlement of Employee Tax Liabilities [Member] | Treasury Stock [Member]              
Equity [Line Items]              
Treasury stock acquired       300,000 300,000    
Value of treasury stock acquired, cost method       $ 9,900,000 $ 11,800,000